“As a result, these specifications still largely follow the rules set forth by the original standard from 1987.”
Nearly every card tap still becomes an ISO 8583 message, a 1987 format of bitmaps, packed BCD and EBCDIC that Visa, Mastercard and Discover each bent into their own dialect. Visa’s Base I has thousands of clients on mainframes and ATMs, so nothing breaking ever ships. A parsing error on an obscure sub-field means a decline at the register. Fintech’s glossy JSON APIs are a translation layer over a 37-year-old wire format.